Pulverizing and classifying machine



1944. H. G. LYKKEN ET AL 6 PULVERIZING AND CLASSIFYING MACHINE.

' Filed July 20, 1959 s Sheets-Sheet 1 v INVENTOR5 MFA/RY 6'. Ly/(KE/V BY W/ //4 H. YK/(f/V M i ATTORNEY.

Nov. 7, 1944. H. G. LYKKEN ET AL PULVERIZING AND CLASSIFYING MACHINE 1939 5 Sheets-Sheet 2 Filed July 20 INVENTORfi MFA/RY 6. LYKKEN L//? H- K/(EN ATTORNEY.

1944. H. G. LYKKEN ET AL PULVERIZING AND CLASSIFYING MACHINE Filed July 20, 1939 3 Sheets-Sheet 3 INVENTORS l/ENRY G. LYKKE/v M k w A.

M A L L Y B ATTORNEY.

Patented Nov. 7, 1944 PULVERIZINGAND CLASSIFYING Ilenry G. Lykhen and William Lykken, 7 Minneapolis; Minn. v

I Application July 20, 1939, Serial No.28 5,48 4 (01. 83-11) rotor a vortex is created around the rotor, due in part to the centrifugal action of the air in front 13 Claims.

Our invention relates to pulverlzing machines and more particularly to such machines for pulverizingand classifying friable materials and delivering the sufliciently pulverized material fro the machine.

Heretofore, in machines of this general character therehas been provided a grinding chamber or zone having therein some means for producing pulverization, such as a rotor or angularly disposed fluid jets, and a separate communicating classifying chamber or zone which receives the sufiiciently pulverized material and some oversize material and wherein the finished material is separated from the over-size, the former being removed from the machine and the latter being returned to the grinding chamber for further reduction in particle size. In such machines it has been diiiicult and expensive to obtain complete separation of the sufficiently pulverized material from that which was over-size so that no over-size material escapes with the finished material, especially where the maximum sizes it was desired to collect were the very fine particle sizes.

Moreover, in machines employing arotor created vortex, such as described in Patent No.

1,836,560, issued December 29, 1931, to Henry G. Lykken, which is the most efllcient and economical method of pulverizing materials, it heretofore has been desirable to have a separate vortex creating element for the separate classifying chamber or zone, especially when the finished product to be delivered was the very fine particle sizes. In such machines, a closed-end fan or 'rotor is used to produce the pulverizing vortex, but that type of rotor has not been necessary in the classifying zone:

In the present machine, we have continued the use of the eflicient principle of vortex pulverizetion by use of a closed-end rotor, but have eliminated the separate classifying chamber or zone with its separate vortex element, and now perform both the pulverizing andthe classifying functions in the same chamber, zone or region. Accordingly, the over-all size of the machine is greatly reduced, the power required is reduced, and at the same time the machine is effective and accurate in classification.

In another view of our invention, we make more efficient use than has heretofore been proposed of centrifugal action for pulverization and centripetal action for classification. The centripetal action is greatly aided, ifnot wholly created by an air current induced axially of the pulverizing rotor. More specifically, with a closed-end 8, 1942, it has been found possible to create additional high speed vortices between the blades of the rotor. We have found now that it is possible to retain the closed-end fan with its accompanying multiple vortex actions and at the same time to induce an air current axially of the rotor which will be approximately equal to the forces creating the vortices, but opposite in phase thereto so that the sufliciently pulverized material is drawn toward the axis of the rotor, then along the axis and out of the rotor chamber, without drawing out over-size particles.

That is to say, the centrifugal action of the rotor blades acts upon the material particles according to the formula --MV where "M" equals the mass of the particles, and -V equals the velocity of the particle, so that the larger the particle the greater is the centrifugal efiect tending to throw it radially from the rotor and to keep it beyond the perimeter of the rotor. It therefore becomes possible to so proportion the induced air current acting oppositely to the centrifugal force for the induced current to carry with it only the material of the desired particle size. Obtaining this desirable result may be facilitated by continuing the rotor blades inwardly to the hub of the rotor and upwardly to the outlet from the rotor chamber so that centrifugal forces are continually acting on the particles being removed to eject any stray over-size particles before they reach the outlet, and also by other structural features as will appear from a more detailed description of our invention. For example, the size and location of the choke ring which defines the outlet from the pulverizing chamber is important.

With some materials and for the even finer particle sizes, it has been found advantageous to change the shape of each rotor blade so as to provide a radial portion adjacent the axis of the rotor and a Joining rearwardly (in the direction of rotation) inclined portion adjacent the periphery of the rotor. This construction of the rotor blades has several operating effects.

When using the axial withdrawing current of air with blades which extend radially only, the centers of rotation of the vortices which occur between the blades are moved inwardly toward the rotor axis.- On the other hand, with the inclined blade portions, these vortices occur adjacent the periphery of the rotor notwithstanding the inwardly and axially moving current of air. With these inner vortices maintained near the periphery of the rotor, the concentration of material therein is kept out of the inner portion of the rotor so that there is less oversize material reaching the center portion of the rotor and consequently less likelihood of any of that material reaching the outlet of the machine.

The degree of inclination of the blade gives a greater throw-out force to the material as it moves across the face of the advancing blade (which is also partly responsible for the relocation of the centers of rotation of the inner vortlces). Accordingly, the particles of material have to move in the direction of the main vortex rotation and also radially a much greater distance before getting into the center of the rotor and from there out of the machine. Only impalpable powder can do that with a high degree of back slant for the outer blade portions and the tendency for larger quantities of the material to enter into the rotor increases as the rearward inclination of the blade approaches the radial.

In addition to the foregoing considerations, there is a somewhat quiescent space behind the knee of each blade, and there is less disturbance in the center portion of the rotor defined by the radial blade portions. The particles of material enter these spaces where they are more freely subject to the withdrawing force of the axial air current. Most of this material will be light enough to be carried out of the machine with that current of air, but such particles as are over-size will be ejected by the centrifugal force within the rotor and then subject to further pulverization.

From the foregoing it will be appreciated that control of fineness of particle size delivered from the machine can now be accomplished by varying the degree of rearward inclination of the rotor blades, as well as by the controls heretofore known of regulating the speed of the main pulverizing vortex and by regulation of the amount of air drawn through the machine.

Our present invention has a further important aspect, viz., particles of many friable materials, such as lithopone, titanium oxide, cocoa, and sulphur, have a tendency to cling together and also to collect or build up in masses on the walls and parts of the machine, and heretofore to such an extent as to interfere with both pulverization and classification, whereas materials of this character are now pulverized efficiently and as thoroughly as other materials that are usually reduced in particle size in a dry state.

This may be due to the considerable quantity of air which passes through the pulverizing zone in a machine of the indicated character, or it may be due in part to some added action by reason of the effect on the various vortices of the axially induced air current.

Machines built according to the constructions hereinafter described and embodying the above principles have been successfully used commercially to pulverize materials to very fine division such as all material delivered being below five microns in size, and even finer sizes experimentally.

Summarized, the objects of our invention may be stated to be to provide a machine in which pulverizing and classifying of friable materials to extremely fine particle sizes may be effectively and efliciently obtained; in which materials heretofore diflicult to pulverize in a dry or semidry state may be pulverized as other dry materials are pulverized; in which both pulverizing and classifying or selecting of the sufiiciently pulverized material takes place in the presence of the pulverizing rotor; in which classification. selection or separation of the material that is sufliciently pulverized is produced almost entirely centripetally in the pulverizing rotor chamber; in which an air, or other fluid, current is induced and acts in opposition to centrifugal forces occurring in the pulverizing zone; in which a closed end fan is used to produce the pulverizing vortex, but classification or selection of the desired product is obtained inwardly and axially of the rotor structure; in which only the sufficiently pulverized material is withdrawn from the pulverizing chamber; and in which the degree of fineness of the material delivered from the machine may be controlled also by variation of the degree of rearward inclination of a portion of each rotor blade.

Other and further objects of our invention will be apparent from this specification taken in conjunction with the accompanying drawings, wherein- Figure 1 is a vertical section through a machine constructed in accordance with our in- Vention;

Fig. 2 is a horizontal section on the line 2-2 of Fig. 1, parts being broken away to facilitate illustration;

Fig. 3 is another horizontal section on the line 3-3 of Fig. 1, parts also being broken away to facilitate the illustration;

Fig. 4 is a cross section of a modified form of rotor, parts being broken away to facilitate illustration; and

Fig. 5 is a, fragmentary detail showing a modified form of seal at the outlet from the rotor chamber.

Certain features of our invention are applicable to pulverizing machines generally, and the embodiments described in this specification are intended to be by way of example only of the application of the foregoing principles. The structures, however, are the best modes in which we have contemplated applying our invention at the present time.

Referring to the drawings, a. hollow base ll supports at one side thereof, an electric motor 12, the shaft of which prcjects into the base and carries a plurality of pulleys l3. A cylindrical casing 14 for the pulverizer is bolted to the other side of the base and is closed at the upper end by top plate IS. The top plate l5 and the base II respectively carry bearings l6 and I! for a vertical shaft I8. The'shaft extends into the base and carries a plurality of pulleys l9 which are driven from the pulleys 13 through belts 2|. As shown the pulleys have a step-up relationship. The pulleys may be selected to obtain any desired speed for the shaft I8 best suited for the particular material being treated.

Within the casing H is a rotor chamber 22 which is closed at its bottom by a dish-shaped plate 23 and at its top by a stationary choke ring 24 which is supported upon the annular flange 24A that is secured to the interior of the casing H.

A rotor, designated generally at 25, is mounted in the chamber 22, and is of less diameter than the casing i4 so as to leave an annular space around the rotor in which space the pulverizing vortex i maintained. The rotor comprises a hub 23, mounted on the shaft i3, a bottom disc 21 secured to the hub 20, and a top ring-shaped disc 23 which is supported upon the outer edges of the radially extending rotor blades 22. The rotor blades extend from the hub 22 to the outer edges of the discs 2'! and 23, and also from the bottom disc to the top of the rotor chamber except for the cut-out outer portions thereof where the ring-shaped top disc 28 is mounted. Eight blades are shown in the drawings, but this number may be varied in accordance with the character of material being pulverized, the size of delivered material desired and the rate of production wanted. The speed of the rotor will also control to some extent the result obtained.

On top of the disc 22 are a plurality of small radial fan blades 3| the purpose of which will be hereinafter described. The fan blades have only a running clearance with the bottom of the choke ring 24. The rotor blades have a wear plate 32 bolted or otherwise secured on the advancing face of each thereof, which extends outwardly slightly beyond the blade, thereby increasing the rotor diameter tothat extent. It is not necessary to our invention to provide the wear plates or to have the same extend beyond the rotor blades.

The space between the choke ring 24 and the top plate It may be termed the delivery chamber 33. The hub 26 extends into that chamber and supports a ring 34 to which is secured a fan composed of the plate 35 on the bottom of which are a plurality of radial blades 36. The number and size of the blades may be varied as desired. Entrance to this delivery chamber of the air and material is obtained through the central opening 31 that is defined by the choke ring 24, and the air and finished material are delivered from the pulverizer through the discharge opening 38 of the chamber 33. It will be understood that the finished material is delivered to a collection system or a for the pulverized material.

Air is admitted to the machine below the bottom plate 23 of the pulverizer through an opening in the side wall of the casing i4, which opening is indicated at 4i. The bottom plate 23 has a central opening 42 therein which is surrounded by an upstanding collar 43. A pair of guides 44 are bolted to the bosses 45 on the bottom of the plate 23, and a pair of plates, one of which is indicated at 48, slides in the grooves 41 which are formed by the guides 44.

The purpose of these. plates is to regulate the size of the opening for the admission of the air to the pulverizing chamber.

On the lower face of the bottom disc 21 of the rotor are a plurality of radial fan blades 43 which are tapered to conform to the shape of the bottom plate 23, and arranged to have a running clearance therewith. Accordingly, the air admitted through the opening 42 is forced out from beneath the rotor through the annular space 49 into the pulverizing zone that is between the rotor blades and the side wall of the casing. This arrangement also provides an air seal at the bottom of the rotor to prevent the entrance of material into the space beneath the rotor, and also to prevent the material from backing up into the air opening and accumulating beneath the bottom plate 23.

With some materials to be pulverized, it has place of use casing as indicated at been found desirable to provide on the inner face of the casing i4 means for retarding the outer portion of the pulverizing vortex of the air supported material both to produce a greater differential of movement between the outer and inner portions of the vortex and also 'to provide a layer of the material on the inner wall of the casing. Accordingly, we have shown the inner wall of the casing provided with a plurality of ribs 5i, which may be in the form of corrugations or in any other suitable form and bolted to the 53 whenever it is desired to use such a lining, as noted above.

The material to be pulverized is introduced into the hopper BI which communicates with a screw type of feeding device indicated at it, the latter being driven by the motor 51 through the sprocket wheels and chain. indicated generally at it. The rate of feed of the material will be regulated by controlling the speed of the motor 51, or by using chine, the air openings are adjusted so that an adequate volume of air will be admitted to the machine, and the motor I2 is started, thus rotating the rotor 25, which, by reason of the relationship of the top and bottom discs of the rotor and the radial blades extending therebetween, sets up a violent vortex in the pulverizing zone around the rotor 25. The motor 51 is then started so as to feed material into this vortex. The material is picked up in the vortex and whirled around in it at high rates of speed, the particles being reduced in size partly by rubbing against each other in the vortex, and partly by innumerable collisions between the particles. Under the action of the centrifugal forces present in the vortex, the particles endeavor to assume a position in the vortex according to their relative masses, with the larger particles along the wall of the casing, and the liner particles adjacent the rotor, where the vortex speed is the highest. With the closed-end rotor the great bulk of the material in the course of pulverization will be kept externally of the rotor, but the sufilciently pulverized material will work its way adjacent the rotor and a portion of the air and the pulverized material will circulate in and out of the spaces between the blades in individual high speed vortices, as noted above.

The fan blades 36 are properly chosen as to size and number to induce a current of air upwardly along the hub 26 of the rotor through the outlet opening 31 in the choke ring 24. In this same connection, the size of the outlet opening is also chosen with respect to the particular volume of air, and the nature of the material being pulverized. In the present construction, this outlet opening is varied by merely placing into the machine choke rings with difl'erent sizes of openings, which can be done readily through the top of the machine. As was stated above, the induced air current is also proportioned in relation to the centrifugal forces created by the rotor 25 so that only the sufllciently pulverized material will be extracted from the rotor chamber. Inasmuch as the rotor blades 29 extend to the hub 28, centrifugal force is constantly acting upon the material that is being drawn axially of the rotor so that any over-size particles are forced outwardly, and by the time the opening 31 is reached, the

material taken out with the air under the action,

of the fan 35 is only that material which is sumciently pulverized according to the design and adjustment of the machine. Usually the opening 31 in the choke ring will be smaller than the opening defined by the ring shaped top disc 28 of the rotor. I

It is a fact also that the air being introduced at the bottom of the vortex zone and rising vertically in the machine through the zone will carry with it the sufficiently pulverized material so that these materials will be drawn inwardly to the axis of the rotor from adjacent the upper part of the rotor. Probably the larger part of the finished material will be obtained from this region. However, the incoming current of air is in ample volume to quickly remove inwardly from the pulverizing zone the sufiiciently pulverized material so that that material does not interfere with the further pulverizing of the other material. The pulverized material reaching the outlet chamber 33 is discharged through the discharge opening 38, as previously explained.

The effect of the axially induced current of air is to draw a larger volume of air from the vortex immediately adjacent the perimeter of the rotor to satisfy the vacuum in back of the rotor blades than would circulate between the rotor blades without the axially induced air current. This action probably produces some disturbing influences in the vortex, which combined with the ample volume of air rising vertically through the pulverizing zone enables the handling in this machine of materials normally not successfully pulverized. except at considerable cost, in a pulverizer of this character, materials such as lithopone, cocoa, etc., referred to above.

In the event any of the over-size material reaches the top of the rotor in the pulverizing zone, it is important that this material does not work its way over the top plate 28 and into the outlet opening 31. The use of the fan blades 3| on top of the disc 28 sets up a sufficient centrifugal force to keep all materials from passing in wardly over the top of the disc 28. The extension of the top disc 28 beyond the edges of the rotor blades 29, or the wear plates 32, assists also in deflecting the materials. Of course, the fan blades 3| are so proportioned and chosen in number as not to interfere with the operation of the machine, it being only necessary to set up enough throw out at the upper edge of the disc 28 to keep materials from reaching the outlet opening 31 over the top of the rotor.

It should be pointed out that we have found it desirable in this machine to increase the height of the rotor over what has heretofore been found suitable for adequate pulverization of friable ma terials to even the very fine particle sizesbelow five microns. and to increase the volume of air introduced into the machine. The height of the rotor has been increased by about one-quarter to one-third its former height, at the rotor speeds used by us, which are approximately 2100 to 2800 R. P. M. with a rotor twenty inches in diameter in the twenty-four inches diameter machine described above.

Referring now to Figs. 4 and 5, there is shown another form of rotor for use in machines operating according to the above principles which has produced improved results in certain cases. The rotor hub 26A is mounted upon the motor driven shaft IBA, and the rotor has a bottom disc 21A, as heretofore described. In this case, however, each rotor blade has a radial portion 6|, which is secured to the hub, and a connecting portion 62 that is inclined rearwardly (with respect to the direction of rotation of the rotor, indicated by the arrow in Fig. 4). These rearwardly inclined or slanting blade portions terminate at the edge of the bottom disc 21A and may or may not be provided with wear plates such as indicated at 32 in Figs. 1 and 2. At the upper end the outer or inclined blade portions are closed by the ring shaped top disc 64.

The degree of rearward inclination of the rotor blades can be as chosen and of course will depend upon a number of variable factors, but the results obtained with the machine can be regulated by the inclination, as determined by tests with blades inclined 30, and from the radial. Insofar as pulverization is concerned, inclining the blades does not destroy the vortex actions, as will be pointed out, but the principal advantages with the slanting blade portions has been noted in connection with the classifier action or separation of the sufliciently pulverized material from that which is the over-size and needs further reduction in particle size.

The action of the rotor blades may be defined as follows: A vacuum is created in back of each of the blades, by the rotation of the rotor, in the exposed area 63, which is determined substantially by the lines A and B (Fig. 4). Line A is tangent to the rotor periphery at the radius line C, which intersects the tip of the blade, and line B is parallel thereto and intersects the tip of the following blade. A pressure is created by the advancing face of each blade and the combined actions is such with the closed rotor ends that the rotor will cause the material and air in the space between the periphery of the rotor and the wall casing to travel in a main pulverizing vortex around'the rotor, as described above.

In addition, in this rotor with the vacuum area 63 as described, the distance between the blades is such that the vacuum and pressure created also causes such air-borne material as enters the space between the blades (to satisfy the vacuum) to whirl in a high-speed vortex in that space and to produce further pulverization. This is akin to the action of the radial blade rotor of Figs. 1-3, and with a proper spacing of the blades this inner vortex action occurs notwithstanding the inclination of the blade portions 62. However, the increased length and the inclining of the blade portions 62 has the efiect of causing the centers of rotation of these vortices to occur somewhat outward from what would be the case with the purely radial blades. It should be pointed out that if the circumferential'spaclng of the blades is such that this inner vortex action does not occur between the blades, then nevertheless the slanting blade portions 62 will keep outwardly toward the periphery of the rotor the concentration of material seeking to enter between the blades.

With the rotor of Figs. 4 and 5, air will be drawn axially through the central opening in the top disc 64 in the same manner as described above in connection with the machine of Figs. 1 to 3, and this action will occur not only axially of the rotor but also inwardly from its periphery. The centers of rotation of the inner vortices, or the centers of concentration of material entering between the blades, will be moved inwardly by this withdrawing air action, but they nevertheless will remain adjacent the periphery of the rotor. That is to say, the proportioning of the force of the air current and the action or the inclined blade portions is such that these centers Near the periphery there is more space for the distribution of the material and air, so that the withdrawin current of air can act thereupon more freely to remove the particles of suiliciently pulverized material into the central part of the rotor and out of the machine. Conversely, there is more room for the withdrawn material to be acted upon by the centrifugal forces of the blade portions 6i and 62 so that over-size material will be thrown out of the rotor more readily and speedily for the needed further pulverization.

Another action of the inclined blade portions which aids in the improved action of this rotor is that the air in the central part of the rotor is disturbed to a considerably less degree than with the purely radial blade. Hence the work of the withdrawing current of air is subjected to less disturbance and becomes more effective in removing quickly the sufficiently pulverized material, and also in removing only the material that has been reduced to the desired particle size. In addition to the quieter central area of the rotor, occupied by the radial blade portions 6|, there is also a quiescent zone 66 behind the knee of each rotor blade into which the withdrawn material tends to enter and to reach a somewhat static condition as it is subjected to the withdrawing air force.

Referring now to Fig. 5, illustrating an improved upper seal, it is seen that the top disc 64 of the rotor extends outwardly adjacent to a ring 61 that is mounted upon the interior of the easing wall l4, and upon which is supported a choke ring 66 which overlies the top disc 64. The disc 64 and the ring 68 have a close running clearance which in many cases will be sufllcient to keep pulverized material from entering the outlet chamber 69 without passing through theaxial opening 65. In addition, to positively seal the opening between disc and choke ring, there is provided an upstanding collar II which is secured to the top disc 64 and also to an upwardly extending portion of the rotor blades 6| so as to be carried with the rotor. A ring 12 of felt or other suitable material is mounted upon the choke ring 68 so as to be in engagement with the projecting portion of the collar ll. Thus the action of the fan 35 is not felt in the space between the top disc 64 and the choke ring 66 and there will be no likelihood of any material, that might get therebetween, passing into the outlet chamber 69.

Other modifications may be made in the arrangement and location of parts within the spirit and scope of our invention, and such modifications are intended to be covered by the al pended claims.

We claim:

1. A pulverizing and classifying machine comprising a motor, a casing having a rotor chamber therein, a rotor mounted in said chamber and spaced from the side walls of said casing to provide a pulverizing zonearound said rotor, the rotor comprising a hub, a bottom disc, radial blades extending from the hub to the outer edge of said disc, and an imperforate ring shaped top disc mounted at the top of said blades so as to close the end of, the rotor at the outer portion thereof, a choke ring mounted immediately above said rotor and extending inwardly from the walls of said casing, the opening in said ring constituting the outlet opening from said rotor chamber,

at least a portion of the rotor blades extending to said outlet opening, an outlet chamber in said rotor,

casing adjacent said choke ring, said chamber with the rotor chamber through said outlet opening, a fan mounted in said outlet chamber and arranged to induce an air current axially of said means for admitting air into said pulverizing zone from beneath said rotor, connections from said motor for operating the rotor and fan, and means for feeding material to be pulverized directly into said pulverizing zone.

2. A pulverizing and classifying machine comprising a motor, a casing having a rotor chamber therein, a rotor mounted in said chamber and spaced from the side walls of said casing to provide a pulverizing zone around said rotor, the rotor comprising a hub, a bottom disc, radial blades mounted upon said disc, and an imperforate ring shaped top disc mounted at the top of said blades so as to close the end oi the rotor at the outer portion thereof and to define a central opening at the top of the rotor, a stationary choke ring mounted immediately above said rotor and extending inwardly from the walls of said casing, the opening in said ring constituting the outlet opening from said rotor chamber and being smaller than and aligned with the opening in the top disc of the rotor, an outlet chamber in said casing adjacent said choke ring, said chamber having a discharge opening and communicating with the rotor chamber through said outlet opening, a fan arranged to induce an air current through said openings, means for admitting air into said pulverizing zone, connections from said motor for operating the rotor and fan, and means for feeding material into said pulverizing zone.

3. A pulverizing and classifying machine comprising a motor, a casing having a rotor chamber therein, a rotor mounted in said chamber and spaced from the side walls of said casing to provide a pulverizing zone around said rotor, the rotor comprising a hub, a bottom disc, blades mounted upon said disc, an imperforate ring shaped top disc mounted at the top of said blades so as to close the end of the rotor at the outer portion thereof, the top disc also extending outwardly beyond the edges of the blades, a stationary choke ring mounted immediately above said rotor and extending inwardly from the walls of said casing, the opening in said ring constituting the outlet opening from said rotor chamber, at least a portion of the rotor blades extending upwardly adjacent to said choke ring, an outlet chamber in said casing adjacent said choke ring, said chamber having a discharge opening and communicating with the rotor chamber through said outlet opening, a fan arranged to induce an air current through said opening, means for preventing material from entering the outlet by passing over the top disc of the rotor, means for admitting air into said pulverizing zone from beneath said rotor, connections from said motor for operating the rotor and fan, and means for feeding material to be pulverized into said pulverizing zone.

4, A pulverizing and classifying machine comprising a motor, a casing having a rotor chamber therein, a rotor mounted in said chamber and spaced from the side walls of said casing to provide a pulverizing zone around said rotor, the rotor comprising a hub, a bottom disc, blades extending inwardly from the outer edge of said disc, said blades having a cut-out portion at the top thereof, an imperforate ring shaped top disc mounted in said cut-out portion, a stationary choke ring mounted immediately above said rotor blades and extending inwardly from the walls of said casing, the opening in said ring constituting the outlet opening from said rotor chamber and registering with the opening in the ring shaped top disc, an outlet chamber in said casing adjacent said choke ring, said chamber having a discharge opening and communicating with the rotor chamber through said outlet opening, a fan arranged to induce an air current through the choke ring and top disc of said rotor, means for admitting air beneath said rotor, a fan for ejecting the air into said pulverizing zone around said rotor, connections from said motor for operating the rotor and fan, and means for feeding material to be pulverized into said pulverizing zone.

5. A pulverizing and classifying machine comprising a motor, a casing, a rotor connected to be operated by said motor and mounted in said casing so as to be spaced from the side walls thereof, said rotor comprising a bottom disc, radial blades mounted thereon, and a top disc for closing a portion of the radial extent of said blades at the'upper edge of said rotor so as to maintain a pulverizing vortex of air and suspended material around said rotor, an opening in the top disc of said rotor, a stationary choke ring mounted in said casing so as to close the space between the rotor and side wall of the casing and having the opening therein registering with the opening in the top disc, means for inducing an air current through said openings to withdraw sufficiently pulverized material inward 1y through said rotor, the withdrawn material being subject to the centrifugal action of the rotor to free the withdrawn material of any oversize material, means for admitting air to said pulverizing vortex, and means for feeding a controlled amount of material to be pulverized to said vortex.

6. A pulverizing machine comprising a hollow base, a motor mounted on the base with its shaft projecting into the base, a casing mounted on the base and having a rotor chamber therein, a rotor mounted in said chamber and spaced from the side walls of the said casing to provide a pulverizing zone around said rotor, the rotor comprising a vertical shaft projecting into the base, operating connections in said base between said shafts, a closed bottom disc mounted on said shaft above the bottom of the rotor chamber, radial blades extending from the shaft to the outer edge of said disc, an imperforate ring-shaped top disc mounted at the top of said blades so as to close the end of the rotor at the outer portion thereof, a stationary choke ring mounted above'the top disc of said rotor and extending inwardly from the walls of said casing, the opening in Said ring constituting the outlet opening from said rotor chamber and registering with the opening in said top disc, an outlet chamber the bottom wall of which is said choke ring, said chamber having a discharge opening, a fan located in said outlet chamber and mounted on said shaft, said fan being arranged to induce an air current through the openings in said ring andthe top disc of said rotor, means for admitting air into said rotor chamber beneath said rotor, a fan connected to said shaft and located beneath said rotor, and means opening into the side wall of said casing for feeding a controlled amount of material to be pulverized into said pulverizing zone.

7. A pulverizing and classifying machine comprising a motor, a casing, a rotor connected to be operated by said motor and mounted in said casing so as to be spaced from the side walls thereof, said rotor comprising a bottom disc, radial blades mounted thereon, and a top disc for closing a portion of the radial extent of said blades at the upper edge of said rotor so as to maintain a pulverizing vortex of air and suspended material around said rotor, an opening in the'top disc of said rotor, a stationary choke ring mounted in said casing so as to close the space between the rotor and side wall of the casing and having the opening therein registered with the opening in the top disc, the opening in the choke ring being of less diameter than the opening in the top disc of said rotor, means for inducing an air current through said openings to withdraw sufficiently pulverized material inwardly through said rotor, the withdrawn material being subject to the centrifugal action of the rotor to free the withdrawn material of any oversize material, means for admitting air to said pulverizing vortex, and means for feeding a controlled amount of material to be pulverized to said vortex.

I 8. A pulverizing and classifying machine com-- prising a motor, a casing, a rotor connected to be operated by said motor and mounted in said casing so as to be spaced from the side walls thereof, said rotor comprising a bottom disc, blades extending inwardly from the periphery of said disc and having an inner radial portion and an outer inclined portion, and a top disc for closing the upper ends of said blades adjacent the periphery of the rotor so that a pulverizing vortex of air and suspended material will be maintained around said rotor, an opening in the rotor top disc, a stationary choke ring mounted in said casing so as to close the space between the rotor and the side walls of the casing and having the opening therein registering with the opening in the top disc, means for inducing an air current through said openings to withdraw sufficiently pulverized material inwardly through said rotor and upwardly along its axis, means for admitting air to said pulverizing vortex, and means for feeding a controlled amount of material to be pulverized to said vortex.

9. A pulverizing and classifying machine comprising a casing, means for feeding air and material to said casing, a motor driven shaft in said casing, a rotor mounted on the shaft and spaced from said casing, said rotorobeing arranged to produce a pulverizing vortex of air and suspended material in said casing externally of said rotor and comprising a closed end, means for closing the opposite end except for an intermediate opening, and blades between said ends arranged to provide a zone near the center of the rotor substantially free from turbulences, and means for withdrawing, selected material into said center zone and through the opening in the rotor end.

10. A pulverizing and classifying machine comprising a casing, a motor driven shaft extending therethrough, a rotor mounted on the shaft to produce a pulverizing vortex in said casing and having a bottom disc, blades on said disc having a radial portion and an outer portion inclined between thirty and sixty degrees with respect to the radial, and a ring shaped upper disc overlying the inclined portions of the blades, means for feeding air and material to said casing, and means for withdrawing air and sufficiently pulverized material through the opening in said ring shaped disc.

11. In a pulverizing and classifying machine, a rotor having a hub, a plurality of blades thereon each having an inner radial portion and an outer portion inclined between thirty and sixty degrees with respect to the radial, a bottom disc, and a ring shaped top disc closing the upper end of the rotor, at least the inclined portions of the'blades being between said discs.

12. A pulverizing and classifying machine comprising a motor, a casing, a chamber therein, a closed end rotor of less diameter than said chamber and mounted therein, the rotor being constructed and arranged to produce a pulverizing vortex of air suspended material in the space around said rotor, means for withdrawing the suificiently pulverized material from said pulverizing vortex into said rotor and axially thereof, an outlet in the upper end of the rotor for the sufliciently pulverized material, operating connections from the motor to the rotor, means for admitting a controlled amount of air into the casing and to the pulverizing vortex, and means for feeding to said vortex a controlled amount of material to be pulverized.

13. A pulverizing and classifying machine comprising a motor, a casing, a rotor connected to be operated by said motor and mounted in said casing so as to be spaced from the side walls thereof, said rotor being constructed and arranged to set up and maintain a pulverizing vortex of air and suspended material around said rotor and comprising a disc adjacent to the bot tom of the casing, radial blades mounted thereon and extending outwardly substantially to the periphery of said disc, a stationary choke ring mounted near the top of said'casing so as to close the space between the rotor and side walls of the casing, the rotor blades operating adjacent the opening in the choke ring, means for inducing an air current through said opening to withdraw sufficiently pulverized material inwardly through said rotor, the withdrawn material being subject to the centrifugal action of the rotor, means for admitting air to said pulverizing vortex, and means for feeding a controlled amount of material to be pulverized to said vortex.

HENRY G. LYKKEN. WILLIAM H. LYKKEN. 

